UK govt skrewed up more like. Agile is a methodology not a magic bullet,the constant iteration works great when you have a solid known backend tech (eg rails) and you are iterating for features and user experience. In this case your technology base is already stable so iterations come easy.
When you are building a technology base from scratch at this scale however you better have a very well thought out data and service model with tested prototypes or you are doomed.
Agile is great at keeping up work flow and communication,forcing reluctant devs to talk to business and forcing business to understand the cost of new features,but if you have architectural problems you wont have the luxury of those communication problems later!
Don't worry - there are still lots of other buzzwords to put your faith blindly into.